notify.c

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#include <uacpi/internal/notify.h>
#include <uacpi/internal/shareable.h>
#include <uacpi/internal/namespace.h>
#include <uacpi/internal/log.h>
#include <uacpi/internal/mutex.h>
#include <uacpi/internal/utilities.h>
#include <uacpi/internal/stdlib.h>
#include <uacpi/kernel_api.h>
#include <uacpi/platform/atomic.h>
 
#ifndef UACPI_BAREBONES_MODE
 
static uacpi_handle notify_mutex;
 
uacpi_status uacpi_initialize_notify(void)
{
    notify_mutex = uacpi_create_native_mutex();
    if (uacpi_unlikely(notify_mutex == UACPI_NULL))
        return UACPI_STATUS_OUT_OF_MEMORY;
 
    return UACPI_STATUS_OK;
}
 
void uacpi_deinitialize_notify(void)
{
    if (notify_mutex != UACPI_NULL)
        uacpi_free_native_mutex(notify_mutex);
 
    notify_mutex = UACPI_NULL;
}
 
struct notification_ctx {
    uacpi_namespace_node *node;
    uacpi_u64 value;
    uacpi_object *node_object;
    uacpi_handle work_item;
};
 
static void free_notification_ctx(struct notification_ctx *ctx)
{
    uacpi_namespace_node_release_object(ctx->node_object);
    uacpi_namespace_node_unref(ctx->node);
 
    /*
     * This is the work item that we're being executed as. Nobody is supposed
     * to be looking at it anymore now that the handler was invoked.
     */
    uacpi_kernel_free_work_item(ctx->work_item);
 
    uacpi_free(ctx, sizeof(*ctx));
}
 
/*
 * The handler lists are only modified with the notify mutex held, but are
 * walked by do_notify without it: a handler is allowed to install another
 * handler, which is not something that it would be able to do otherwise.
 *
 * This is safe because a handler is fully initialized before it's linked in,
 * and because an unlinked handler is only freed after all of the in-flight
 * notifications that might still be looking at it have finished.
 */
static uacpi_device_notify_handler *load_handler(
    uacpi_device_notify_handler **handler
)
{
    return (uacpi_device_notify_handler*)uacpi_atomic_load_ptr(handler);
}
 
static void do_notify(uacpi_handle opaque)
{
    struct notification_ctx *ctx = opaque;
    uacpi_device_notify_handler *handler;
    uacpi_bool did_notify_root = UACPI_FALSE;
 
    handler = load_handler(&ctx->node_object->handlers->notify_head);
 
    for (;;) {
        if (handler == UACPI_NULL) {
            if (did_notify_root) {
                free_notification_ctx(ctx);
                return;
            }
 
            handler = load_handler(
                &g_uacpi_rt_ctx.root_object->handlers->notify_head
            );
            did_notify_root = UACPI_TRUE;
            continue;
        }
 
        handler->callback(handler->user_context, ctx->node, ctx->value);
        handler = load_handler(&handler->next);
    }
}
 
uacpi_status uacpi_notify_all(uacpi_namespace_node *node, uacpi_u64 value)
{
    uacpi_status ret;
    struct notification_ctx *ctx;
    uacpi_object *node_object;
 
    node_object = uacpi_namespace_node_get_object_typed(
        node, UACPI_OBJECT_DEVICE_BIT | UACPI_OBJECT_THERMAL_ZONE_BIT |
              UACPI_OBJECT_PROCESSOR_BIT
    );
    if (uacpi_unlikely(node_object == UACPI_NULL))
        return UACPI_STATUS_INVALID_ARGUMENT;
 
    ret = uacpi_acquire_native_mutex(notify_mutex);
    if (uacpi_unlikely_error(ret))
        return ret;
 
    if (node_object->handlers->notify_head == UACPI_NULL &&
        g_uacpi_rt_ctx.root_object->handlers->notify_head == UACPI_NULL) {
        ret = UACPI_STATUS_NO_HANDLER;
        goto error_out;
    }
 
    ctx = uacpi_kernel_alloc(sizeof(*ctx));
    if (uacpi_unlikely(ctx == UACPI_NULL)) {
        ret = UACPI_STATUS_OUT_OF_MEMORY;
        goto error_out;
    }
 
    ctx->work_item = uacpi_kernel_create_work_item();
    if (uacpi_unlikely(ctx->work_item == UACPI_NULL)) {
        uacpi_free(ctx, sizeof(*ctx));
        ret = UACPI_STATUS_OUT_OF_MEMORY;
        goto error_out;
    }
 
    ctx->node = node;
    // In case this node goes out of scope
    uacpi_shareable_ref(node);
 
    ctx->value = value;
    ctx->node_object = uacpi_namespace_node_get_object(node);
    uacpi_object_ref(ctx->node_object);
 
    /*
     * Nothing prevents the kernel from executing the work synchronously, e.g.
     * because it sees no reason to defer it if it's not in an interrupt
     * context. The handlers are free to call back into uACPI, be it to
     * evaluate an object or to install another handler, so make sure that
     * we're not holding onto anything that they might need. This includes the
     * namespace, which is locked by whoever is sending the notification.
     *
     * Everything that the work needs is referenced by now, and there's nothing
     * left for us to do after it's scheduled.
     */
    uacpi_release_native_mutex(notify_mutex);
    uacpi_namespace_write_unlock();
 
    uacpi_kernel_schedule_work(
        UACPI_WORK_NOTIFICATION, ctx->work_item, do_notify, ctx
    );
 
    uacpi_namespace_write_lock();
    return UACPI_STATUS_OK;
 
error_out:
    uacpi_release_native_mutex(notify_mutex);
    return ret;
}
 
static uacpi_device_notify_handler *handler_container(
    uacpi_handlers *handlers, uacpi_notify_handler target_handler
)
{
    uacpi_device_notify_handler *handler = handlers->notify_head;
 
    while (handler) {
        if (handler->callback == target_handler)
            return handler;
 
        handler = handler->next;
    }
 
    return UACPI_NULL;
}
 
uacpi_status uacpi_install_notify_handler(
    uacpi_namespace_node *node, uacpi_notify_handler handler,
    uacpi_handle handler_context
)
{
    uacpi_status ret;
    uacpi_object *obj;
    uacpi_handlers *handlers;
    uacpi_device_notify_handler *new_handler;
 
    UACPI_ENSURE_INIT_LEVEL_AT_LEAST(UACPI_INIT_LEVEL_SUBSYSTEM_INITIALIZED);
 
    if (node == uacpi_namespace_root()) {
        obj = g_uacpi_rt_ctx.root_object;
    } else {
        ret = uacpi_namespace_node_acquire_object_typed(
            node, UACPI_OBJECT_DEVICE_BIT | UACPI_OBJECT_THERMAL_ZONE_BIT |
                  UACPI_OBJECT_PROCESSOR_BIT, &obj
        );
        if (uacpi_unlikely_error(ret))
            return ret;
    }
 
    ret = uacpi_acquire_native_mutex(notify_mutex);
    if (uacpi_unlikely_error(ret))
        goto out_no_mutex;
 
    handlers = obj->handlers;
 
    if (handler_container(handlers, handler) != UACPI_NULL) {
        ret = UACPI_STATUS_ALREADY_EXISTS;
        goto out;
    }
 
    new_handler = uacpi_kernel_alloc_zeroed(sizeof(*new_handler));
    if (uacpi_unlikely(new_handler == UACPI_NULL)) {
        ret = UACPI_STATUS_OUT_OF_MEMORY;
        goto out;
    }
 
    new_handler->callback = handler;
    new_handler->user_context = handler_context;
    new_handler->next = handlers->notify_head;
 
    uacpi_atomic_store_ptr(&handlers->notify_head, new_handler);
 
out:
    uacpi_release_native_mutex(notify_mutex);
out_no_mutex:
    if (node != uacpi_namespace_root())
        uacpi_object_unref(obj);
 
    return ret;
}
 
uacpi_status uacpi_uninstall_notify_handler(
    uacpi_namespace_node *node, uacpi_notify_handler handler
)
{
    uacpi_status ret;
    uacpi_object *obj;
    uacpi_handlers *handlers;
    uacpi_device_notify_handler *prev_handler, *containing = UACPI_NULL;
 
    UACPI_ENSURE_INIT_LEVEL_AT_LEAST(UACPI_INIT_LEVEL_SUBSYSTEM_INITIALIZED);
 
    if (node == uacpi_namespace_root()) {
        obj = g_uacpi_rt_ctx.root_object;
    } else {
        ret = uacpi_namespace_node_acquire_object_typed(
            node, UACPI_OBJECT_DEVICE_BIT | UACPI_OBJECT_THERMAL_ZONE_BIT |
                  UACPI_OBJECT_PROCESSOR_BIT, &obj
        );
        if (uacpi_unlikely_error(ret))
            return ret;
    }
 
    ret = uacpi_acquire_native_mutex(notify_mutex);
    if (uacpi_unlikely_error(ret))
        goto out_no_mutex;
 
    handlers = obj->handlers;
 
    containing = handler_container(handlers, handler);
    if (containing == UACPI_NULL) {
        ret = UACPI_STATUS_NOT_FOUND;
        goto out;
    }
 
    prev_handler = handlers->notify_head;
 
    // Are we the last linked handler?
    if (prev_handler == containing) {
        uacpi_atomic_store_ptr(&handlers->notify_head, containing->next);
        goto out;
    }
 
    // Nope, we're somewhere in the middle. Do a search.
    while (prev_handler) {
        if (prev_handler->next == containing) {
            uacpi_atomic_store_ptr(&prev_handler->next, containing->next);
            goto out;
        }
 
        prev_handler = prev_handler->next;
    }
 
out:
    uacpi_release_native_mutex(notify_mutex);
out_no_mutex:
    if (node != uacpi_namespace_root())
        uacpi_object_unref(obj);
 
    if (uacpi_likely_success(ret)) {
        /*
         * The handler is no longer reachable, but a notification that started
         * before we unlinked it might still be about to call it. Wait for
         * those to finish, this also guarantees that the handler is never
         * invoked again after we return.
         *
         * This must be done without the notify mutex held: the work that we
         * are waiting for needs it in order to dispatch a Notify().
         */
        uacpi_kernel_wait_for_work_completion();
        uacpi_free(containing, sizeof(*containing));
    }
 
    return ret;
}
 
#endif // !UACPI_BAREBONES_MODE